This invention relates to fuel filter/separators. More specifically, this invention relates to fuel filter/separators and an associated end cap design which will accommodate fuel flow in different directions.
As used herein, "fuel filter", "filter unit", and "filter media" shall include devices which separate liquid contaminants from fuel, commonly referred to as separators, in addition to devices for removing particulate contaminants from fuel.
The use of fuel filters for separating contaminants from fuel is well known in the art. Many filters are of the spin-on type and may conveniently be screwed onto a head or an engine block which simply supply fuel to the filter and allow fuel to exit from the filter unit. Typically, the filters are cylindrical and include annular or cylindrical filter media within the unit. Commonly, the cylindrical filter media is disposed within a metallic casing and is supported by a end cap which may be made of plastic.
At least some prior art filter unit designs have included provisions for a prefiltering contaminant collection zone or sump. Such a sump is used to collect especially heavy contaminants which may drop out of the fuel prior to its passage through the filter media. Such prefiltering contaminant collection zones or sumps are advantageous in prolonging the life of the filter. Additionally, such sumps are used for collecting water or other liquid contaminants which are separated from the fuel by barrier filters. Alternately, some designs use a collection sump for coalesced water on the downstream side of a coalescing filter media.
Traditionally, the majority of spin-on filters have used an outside-in flow through the annular or cylindrical filter media. This provides the maximum surface area such that particulate matter will not clog the filter as easily as with a reduced surface area such as radially outward flow.
In contrast to the radially inward flow of the filters for particulate matter, coalescing filters have generally used flow from the interior of the cylindrical filter to flow radially outward. The radially outward flow causes a decrease in velocity which tends to aid the coalescing action of the coalescing filter media.
Regardless of whether a spin-on filter unit uses radially outward flow or radially inward flow, it is screwed onto the head or engine block which supplies fuel to the fuel inlet port or ports on the filter unit and which receives fuel from the fuel outlet port or ports on the filter unit. Because the head is arranged for either radially inward flow or radially outward flow, the filter unit screwed into the head must be compatible with it.
Compatibility between a filter unit and the head in which it is to be screwed to is especially important if the filter unit includes a sump for the purposes described above. Obviously, if the sump is designed to be a prefiltering sump and the fuel flow is reversed, the sump will no longer function in its intended fashion.
The present inventor was a coinventor with William G. Nostrand of an invention which allows a coalescer using radially outward flow to be connected to a head or engine block which is designed for radially inward flow. That invention, which is described in detail in U.S. Pat. No. 4,292,179 issued on Sept. 29, 1981 and entitled "Spin-On Filter Coalescer Unit With Flow Reversing Baffle Assembly", uses a flow reversing baffle assembly to allow a radially outward flow filter to be used in a head or engine block constructed to supply fuel to a radially inward flow filter.
Previous U.S. patents further include the following:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 3,228,527 McPherson Jan. 11, 1966 3,312,351 Kasten April 4, 1967 3,726,403 Shaltis April 10, 1973 3,859,216 Sisson et al. Jan. 7, 1975 ______________________________________
The McPherson patent shows a water separating fuel filter having an embodiment for radially outward flow of the fuel with outlets to a single collection sump and an alternate radially inward flow embodiment having outlets for passing contaminants into a collection zone or sump.
The Kasten patent shows a fuel filter/separator with radially outward flow and a single sump which receives coalesced water from the outside layer of a filter media.
The Shaltis patent shows a spin-on fuel filter having dual flow paths such that the fuel initially passes radially outward from an annular filter media. Some of the fuel flows down and up a lower contaminant collection area whereas the rest of the fuel flows radially inward.
The Sisson et al. patent discloses a filter assembly having radially inward fluid flow and a single contaminant collection zone. A relief valve is two-way to permit fluid flow in either direction depending upon the direction of fluid flow through the element.
The use of a dual collection zone or sump arrangement with a spin-on filter is disclosed in U.S. patent application No. 568,271 filed by Wilson et al. on Jan. 3, 1984 under the title "Filter Assembly", now U.S. Pat. No. 4,502,956 issued on Mar. 5, 1985. That application, which is a continuation of application Ser. No. 351,761 filed on Feb. 24, 1982, now abandoned, is assigned to the assignee of the present invention and is hereby incorporated by reference. The Wilson et al filter design includes an inner and an outer cylindrical filter media. A central contaminant collection zone or sump is adapted to receive contaminants prior to fuel passage through the inner filter media, whereas an annular contaminant collection zone or sump is adapted to receive contaminants after the fuel has passed through the coalescing inner filter media.
Although the previous filter designs have been generally useful, their flexibility in use has been limited. Likewise, the end caps used for such filter designs have been limited in flexibility.